A method for fabricating a semiconductor memory device is described. An
insulating layer is disposed on a semiconductor substrate. A matrix of
semiconductor memory elements is disposed in the substrate. The
semiconductor memory elements include a plurality of contact holes formed
in the insulating layer. One contact hole is formed in the insulating
layer for each of the semiconductor memory elements. A bit definition
region is disposed in the semiconductor substrate underneath each of the
contact holes. A contact plug is disposed in each of the contact holes
and is in electrical contact with the bit definition region. The bit
definition region is configured such that a contact resistance between
the semiconductor substrate and the contact plug defines a bit to be
stored in the semiconductor memory elements, An evaluation circuit is
connected to and evaluates the contact resistance of the semiconductor
memory elements.